Jetstar Australia has confirmed that two senior executives from its Vietnamese franchise, Jetstar Pacific, are being questioned by authorities and are not allowed to leave Vietnam.

Jetstar Pacific's chief operating officer, Daniela Marsilli, and its chief financial officer, Tristan Freeman, are assisting Vietnamese authorities in relation to the loss of almost AU$34 million linked to petrol reserves costs.

Former chief executive of Jetstar Pacific, Luong Hoia Nam, was arrested on Jan. 7 as part of the investigation into the airline.

Australian Department of Foreign Affairs and Trade (DFAT) says it raised the issue of the Australian executives with Vietnam's ambassador to Australia in Canberra on Dec. 24.

The department is working with the Vietnamese embassy in Hanoi to get more details on why the two Australian executives are being refused permission to leave the country.